We are using the TPS61020 to convert 3.3V to 5V.
We have placed a 4.7pf capacitor across the upper resistor branch of the feedback resistor divider.
This capacitor was placed there per recommendation from the TPS61020 datasheet (Sept 2003, page 16, under “Small Signal Stability” which reads…
The missing ESR can be compensated in the feedback divider. Typically, a capacitor in the range of 4.7pf in parallel to R3 helps to obtain small signal stability with lowest ESR output capacitors.
However, with this capacitor in place we see an anomaly. Probably half of the time, the TPS61020 will power up outputting ~4.7 volts instead of 5 volts and stays there. When in this state all pin values are identical to those of a part that is running at 5 volts, including FB (at 500mV).
When we remove the 4.7pf capacitor, the TPS61020 comes up at 5 volts every time!
Has anyone else ever seen this anomaly? We are considering removing the 4.7pf capacitor. Any concerns with this action?
